In modern sewing machines, particularly of the industrial type, it is frequently desirable to use high speed operation. When using high speed operations, however, a problem may result in that moving parts within the frame of the machine have a tendency to overheat, with resulting deterioration of lubricant and parts of the machine. Lubricating systems have been suggested in which there is provided means for supplying lubricant to the various areas of the machine, but without any regard for the quantities of lubricant that are being delivered to the various mechanisms. In this regard, these known systems have the drawback of supplying surplus quantities of lubricant in order to insure lubrication of the bearings and bushings of and, thus, there is great likelihood of excess lubricant leaking from the bearing surfaces, not only when the machine is running, but also after the machine has come to a stop. In addition, an excess amount of lubricant means that reduntant work is being done in supplying excessive or unnecessary power consumption. Excess heat at the bearing may also occur as a result of surplus lubricant being supplied to the bearing.
The quantity of lubricant required by one specific mechanism, i.e. the feed mechanism of the machine, may be different from that required by another mechanism, i.e. the drive mechanism for an operating tool. It has been found that the quantity of lubricant required for or by each mechanism is dependent upon such variable factors as the dynamic loading characteristics of the mechanism, the desired rate of heat removal, the type of bearings used, etc. Besides its function of reducing friction between bearing components, lubrication may also help to protect the bearings or bushings from corrosion and act as the heat transferring media. To best accomplish these purposes, it is essential that the quantity of lubricant be accurately adapted to the conditions under which the bearings and lubricant must operate. As mentioned, too much lubricant may result in excessive heat generation due to shearing the excess amount of lubricant supplied. Too little lubricant may not maintain an adequate lubricating film within the bearing which may result in abnormal wear and heat build-up. For the reasons discussed herein above, it has been found necessary to conceive and develop a lubrication system which will satisfy all of the requirements set forth above and overcome the drawbacks of the prior systems.